Guillain-Barré syndrome is divided into two major subtypes, acute inflammatory demyelinating polyneuropathy and acute motor axonal neuropathy. The characteristic electrophysiological features of acute motor axonal neuropathy are reduced amplitude or absence of distal compound muscle action potentials indicating axonal degeneration. In contrast, autopsy study results show early nodal changes in acute motor axonal neuropathy that may produce motor nerve conduction block. Because the presence of conduction block in acute motor axonal neuropathy has yet to be fully recognized, we reviewed how often conduction block occurred and how frequently it either reversed or was followed by axonal degeneration. Based on Ho's criteria, acute motor axonal neuropathy was electrodiagnosed in 18 patients, and repeated motor nerve conduction studies were carried out on their median and ulnar nerves. Forearm segments of these nerves and the across-elbow segments of the ulnar nerve were examined to evaluate conduction block based on the consensus criteria of the American Association of Electrodiagnostic Medicine. Twelve (67%) of the 18 patients with acute motor axonal neuropathy had definite (n=7) or probable (n=5) conduction blocks. Definite conduction block was detected for one patient (6%) in the forearm segments of both nerves and probable conduction block was detected for five patients (28%). Definite conduction block was present across the elbow segment of the ulnar nerve in seven patients (39%) and probable conduction block in two patients (11%). Conduction block was reversible in seven of 12 patients and was followed by axonal degeneration in six. All conduction blocks had disappeared or begun to resolve within three weeks with no electrophysiological evidence of remyelination. One patient showed both reversible conduction block and conduction block followed by axonal degeneration. Clinical features and anti-ganglioside antibody profiles were similar in the patients with (n=12) and without (n=6) conduction block as well as in those with (n=7) and without (n=5) reversible conduction block, indicating that both conditions form a continuum; a pathophysiological spectrum ranging from reversible conduction failure to axonal degeneration, possibly mediated by antibody attack on gangliosides at the axolemma of the nodes of Ranvier, indicating that reversible conduction block and conduction block followed by axonal degeneration and axonal degeneration without conduction block constitute continuous electrophysiological conditions in acute motor axonal neuropathy.

Cardiac 123I-MIBG findings are similar among idiopathic RBD and the syndromes of PD and DLB, but differ from those of PSP and MSA.

ScientiFic inveStigAtionSStudy objectives: We investigated the prevalence of silent cerebrovascular lesions in patients with obstructive sleep apnea (OSA) and the correlation between OSA severity and prevalence of silent cerebrovascular lesions in Japanese patients. Methods: Study subjects were 192 polysomnography (PSG)-confirmed patients who visited the sleep disorders clinic in our university hospital. None had a history of cerebrovascular disease (CVD). We performed a cross-sectional study on OSA severity and the prevalence of silent cerebrovascular lesions detected by brain MRI analysis. Results: The control (AHI < 5/h) group included 19 subjects with a mean AHI of 1.7 ± 1.6/h, the mild OSAS (AHI 5 to < 15/h) group included 25 patients with a mean AHI of 9.5 ± 3.7/h, the moderate OSAS (AHI 15 to < 30/h) group included 35 patients with a mean AHI of 22.0 ± 7.0/h while the severe OSAS (AHI ≥ 30/h) group included 113 patients with a mean AHI of 59.9 ± 20.5/h. A larger percentage of patients with severe OSAS had a higher BMI and hyperglycemia than those with mild or moderate OSAS and control subjects (p < 0.05).Silent lacunar infarction was identified in 4 (21.1%) control subjects, 3 (12.0%) patients with mild OSA, 17 (48.6%) with moderate OSA and 61 (54.0%) with severe OSA. Among control subjects and the mild, moderate, and severe OSA groups, 4 (21.1%), 5 (20.0%), 19 (54.3%) and 61(54.0%), respectively, had periventricular hyperintensity (PVH); most PVH was mild to moderate. conclusion: Results indicate that patients with moderate to severe (AHI ≥ 15/h) OSA have a higher prevalence of silent cerebrovascular lesion than those with less severe OSA.

A 67-year-old woman with Parkinson's disease (PD) was being treated with cabergoline. Her excessive daytime sleepiness (EDS) worsened and sleep episodes appeared one week after her medication was changed to pergolide. We speculate that the cause was the change in dopamine agonists that caused a difference in the affinities of the dopamine receptors that affect the sleep-wake mechanism, or an individual difference in sensitivity to dopamine agonists. In treating PD it is necessary to attend to the appearance of sleep episodes or worsening EDS when changing medication from a dopamine agonist to the same type of ergot dopamine agonist.

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P i c t u r e 1 . B r a i n c o mp u t e d t o mo g r a p h y s h o ws t h e d i l a t e d f o u r t h v e n t r i c l e a n d l a t e r a l v e n t r i c l e s ( a r r o ws ) .P i c t u r e 2 . T 1 -we i g h t e d ( T E / T R= 4 5 0 / 1 4 ms e c ) ma g n e t i c r e s o n a n c e i ma g e s ( MRI ) s h o w t h e s y r i n x c a v i t y i n v o l v i n g t h e e n t i r e s p i n a l c o r d a n d c e r e b e l l a r t o n s i l l a r h e r n i a t i o n ( A, C: S a g i t t a l MRI , B : Ax i a l MRI a t C6 l e v e l ) . PICTURES IN CLINICAL

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